Modular muffler

ABSTRACT

An exhaust gas muffler for an engine, the exhaust gas muffler having: a body, at least one inlet for the exhaust gas from the engine on the body, a chamber in the body to receive exhaust gas from the at least one exhaust gas inlet and to reduce a sound of the exhaust gas, and at least one exhaust gas outlet from the chamber to vent the exhaust gas from the chamber, the exhaust gas outlet being sized and shaped to receive a sound reducing element from outside of the muffler, wherein, by attaching a sound reducing element to the muffler, the muffler can reduce the sound of the exhaust gas to a predetermined level.

CROSS-REFERENCE TO RELATED APPLICATIONS

Not applicable.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH

Not applicable.

FIELD OF THE INVENTION

This invention relates to the general field of exhaust systems, and more particularly to mufflers used with internal combustion engines.

BACKGROUND OF THE INVENTION

Internal combustion engines generate by products of combustion often referred to as exhaust gases. Typically, for noise control the exhaust gases pass through a muffler and tailpipe before being released. Such engines and their associated exhaust systems are ubiquitous, being used to power all types of motor vehicles as well as smaller, more specialized vehicles and devices such as, for example, golf carts, all-terrain vehicles (ATV's), utility vehicles, lawn tractors and mowers, power generators, and other turf and industrial equipment.

The degree of sound absorption or muffling performed by a particular muffler will vary depending on the type of vehicle, engine, or device, and its application. For example, a muffler used in an ATV may need to perform less attenuation than one used in a golf cart, since the expected noise level for the ATV is likely to be higher than that for the golf cart.

In some situations it would be desirable for a particular vehicle or device to be available with more than one sound output level. This may occur, for example, with a product distributed in different markets having different regulatory levels of permissible engine noise. Alternatively, a segment of users within a common target market may be willing to pay extra for quieter devices. In another case, a manufacturer may wish to increase efficiency and reduce cost by using the same muffler in more than one of its products that have different noise reduction requirements.

Structurally, most mufflers contain an inlet to receive exhaust gas, a chamber containing a variety of components, and an outlet to vent the gas. The sound reduction or attenuation capability of a particular muffler is generally determined by the size, shape, number, and nature of components that may be present in the chamber, and by the size and number of exhaust inlets and outlets. Further, since exhaust gases are usually extremely hot and move under pressure at high velocity, the muffler chambers are almost always very tightly sealed by thorough welding or mechanical forming of joints and seams.

As a result of this structure, once mufflers are manufactured they cannot be opened, and the degree of sound attenuation remains fixed at the level originally designed. Applications or devices that have different muffling requirements therefore must specify a different muffler for each desired attenuation level. Since each muffler must be separately designed, produced, and distributed, this is costly and inefficient.

SUMMARY OF THE INVENTION

What is desired is a muffler which overcomes one or more of the above problems.

The muffler should preferably be configured so that it can be modified, at a time after it has been manufactured and sealed closed, to obtain a higher degree of sound absorption or attenuation. Preferably, the modification can be done quickly and easily, and from outside the muffler so that the muffler would not have to be opened. The modification will preferably be sufficiently strong and effective so that it is permanent, unless the user wishes to remove the modification, without requiring further action to maintain the enhanced level of sound reduction. It is also preferable that the muffler be capable of manufacture using standard production methods.

The muffler will preferably be modular, comprising a base muffler having an intrinsic sound reducing capability, and a sound reducing element that can be inserted into or attached to the base muffler, to further reduce the sound output of the muffler. By selecting from different sound reducing elements spanning a range of attenuation levels, the sound reduction capability of the muffler can be improved to a predetermined level without making any changes to the base muffler.

Accordingly, there is provided an exhaust gas muffler for an engine, said exhaust gas muffler having a body; at least one inlet for said exhaust gas from said engine on said body; a chamber in said body to receive exhaust gas from said at least one exhaust gas inlet and to reduce a sound of said exhaust gas; and at least one exhaust gas outlet from the chamber to vent said exhaust gas from said chamber, said exhaust gas outlet being sized and shaped to receive a sound reducing element from outside of said muffler, wherein, by attaching a sound reducing element to said muffler, said muffler can reduce said sound of said exhaust gas to a predetermined level.

BRIEF DESCRIPTION OF THE DRAWINGS

Reference will now be made, by way of example only, to preferred embodiments of the invention as illustrated in the attached figures.

FIG. 1 is a side view of the modular muffler of the present invention, showing a base muffler and a sound reducing element;

FIG. 2 is a side view of the modular muffler of FIG. 1, showing the sound reducing element inserted into the base muffler;

FIG. 3 is a side view of another embodiment of the modular muffler, in which the base muffler has a substrate in the exhaust gas conduit;

FIG. 4 is a side view of another embodiment of the modular muffler, in which the base muffler has a substrate in the chamber; and

FIG. 5 is a side view of another embodiment of the modular muffler, in which the sound reducing element has a substrate.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The modular muffler or exhaust gas muffler of the present invention is shown in a side view in FIG. 1 and generally designated as 10. The muffler 10 receives exhaust gas 11 from an engine (not shown). The muffler 10 generally comprises a base muffler or body 12 having at least one exhaust gas inlet 14, an internal chamber 16 to receive the exhaust gas 11 from the inlet 14, and at least one exhaust gas outlet or tailpipe 18 to vent the exhaust gas from the chamber 16. In the embodiments shown in FIGS. 1-5 there are two exhaust gas inlets 14. The chamber 16 has a first or back wall 20 at one end and a second or front wall 22 at the other end. In the figures the tailpipe 18 is attached to back wall 20, and extends the length of the chamber 16 past front wall 22 to a termination point 24 outside of body 12. The tailpipe 18 is usually configured as a tube or conduit, although other embodiments are also comprehended by the present invention.

The muffler 10 also includes a sound reducing element or insertable inner conduit 26, shown to the right of the base muffler 12 in FIG. 1. The inner conduit 26 may include attachment means or seal rings 28. The exhaust gas outlet or tailpipe 18 is sized and shaped to receive or attach to the sound reducing element 26 from outside of the muffler. It can be seen in FIG. 1 that the conduit 26 is narrower than tailpipe 18. FIG. 2 shows conduit 26 inserted inside tailpipe 18. The conduit 26 rests securely inside tailpipe 18 and resists removal due to attachment means 28, or more particularly, due to a friction fit between seal rings 28 and tailpipe 18.

In FIGS. 1 and 2 both tailpipe 18 and conduit 26 have perforations or louvres 30 along their length. For clarity, the louvres are represented by diagonal lines intersecting the surface of the tailpipe 18 or conduit 26. The louvres provide openings through which exhaust gas 11 can enter or exit the respective tubes or conduits.

FIG. 1 shows exhaust gas 11 entering base muffler 12 at inlets 14, circulating within chamber 16 and exiting the muffler 12 through tailpipe 18. It can be appreciated that this configuration of the chamber 16 and body 12 will result in a degree of noise reduction or attenuation of the exhaust gas 11. In FIG. 1 inner conduit 26 is outside base muffler 12, but can be inserted into the base muffler by moving it as shown by arrow 15.

FIG. 2 shows the same base muffler 12 as FIG. 1, but after inner conduit 26 has been inserted and attached to the tailpipe 18. Accordingly, in FIG. 2 the flow of exhaust gas 11 through muffler 10 is varied by the presence of inner conduit 26 inside tailpipe 18. It is a feature of the present invention that the configuration of FIG. 2 provides a higher degree of sound reduction, absorption, or attenuation than that provided by the base muffler of FIG. 1 alone. Moreover, it can be appreciated that by attaching different sound reducing elements 26 having different levels of attenuation to the base muffler, the muffler 10 can be configured to produce a predetermined level of sound reduction or attenuation.

The base muffler 12 contains the body 12, gas inlet 14, chamber 16 in the body to receive the exhaust gas 11 from the gas inlet 14, and tailpipe 18 to vent the exhaust gas 11 from the chamber 16. It can be appreciated that these elements are generally standard components of engine mufflers. The present invention comprehends a wide variety of configurations of the base muffler 12 as long as the function of sound reduction or attenuation is accomplished. For example, the chamber 16 may contain one or more baffles or other components (not shown in the figures). The tailpipe 18 may have an open end inside the chamber 16 rather than extend to back wall 20, and may have louvres along any portion of its length, including no louvres if desired. The body 12 is preferably oval or round at the ends and rectangular along its length, but other shapes are comprehended as well.

The base muffler 12, or more particularly the tailpipe 18 of base muffler 12, is also sized and shaped to receive the sound reducing element 26 from outside of the base muffler 12. For example, where the conduit 26 has a certain diameter, the tailpipe 18 may comprise a conduit having a larger diameter than that of the conduit 26. In this way, the tailpipe 18, or more broadly the base muffler 12, will be sized and shaped to receive the conduit 26.

In the figures the conduit 26 includes attachment means or seal rings 28. In their preferred form, the seal rings are made of a mica compound. When the rings are heated, such as occurs during normal operation of the muffler, the molecular structure of the rubber rings changes and causes them to expand and form a seal. Accordingly, the tailpipe 18 may be sized and shaped to receive the conduit 26 having seal rings. The tailpipe 18 will have a sufficiently large diameter so that the conduit 26 can be inserted into the tailpipe 18 for its full or partial length. At the same time, the tailpipe diameter will be small enough so that when the seal rings expand, they will press tightly against the inner diameter of the tailpipe 18 so that the conduit 26 is securely held with a tight friction fit. Instead of expanding seal rings, a mechanical friction fit form may be used. For example, the inner conduit 26 may be crimped so that the inner conduit 26 and tailpipe 18 attach by a metal-on-metal friction fit.

The present invention also comprehends placing the attachment means 28 in the tailpipe 18 rather than the conduit 26. Any type of attachment means may be used as long as it functions to secure the sound reducing element 26 to the exhaust gas outlet 18. Where the attachment means 28 is part of the tailpipe 18, the tailpipe 18 and attachment means 28, or base muffler 12, would similarly be sized and shaped to receive the conduit 26. Other types of attachment means 28 may include, for example, a knitted gasket, a clamp or bolt connection at the termination point 24, or a pin and slot or screw arrangement.

The sound reducing element or insertable inner conduit 26 is any device or structure having a body sized and shaped to fit inside the exhaust gas outlet or tailpipe 18 of the base muffler 12, and to attach securely to the tailpipe 18 through an attachment means 28. The invention also comprehends attaching conduit 26 to the end of tailpipe 18 without inserting the conduit 26 inside the tailpipe. Preferably the sound reducing element 26 comprises a hollow tube or conduit, since that forms a convenient fit inside a tubular tailpipe, and provides a path for exhaust gases to pass through. However, it can be appreciated that other forms of sound reducing element 26 may be used. In the figures, a spark arrestor 32 is shown at the end of conduit 26.

The inner conduit 26 may include louvres, perforations, or holes having different size openings, along all or a portion of its length. It may contain baffles or other sound attenuating materials. The conduit 26 is preferably the full length of the chamber 16, but may be shorter to any degree as well. Also, the diameter of the conduit 26 may vary from approximately the same as the tailpipe 18 to a diameter that is much smaller. It can be appreciated that the sound reduction capability of the inner conduit 26 will vary depending on the configuration of a particular unit.

It can therefore be appreciated that by inserting different conduits 26 having different configurations into a single common base muffler 12, the sound output from the muffler 10 will vary over a range. More particularly, a predetermined sound output level can be obtained from a single base muffler by careful selection of the inner conduit 26.

The modular muffler of the present invention is shown in FIG. 2 with the conduit 26 fully inserted into the base muffler 12. It can be seen that the conduit 26 is secured to the tailpipe 18 by the expanded seal rings 28, located close to either end of the conduit 26. Exhaust gas 11 flows into tailpipe 18 through the louvres 30 and then flows either into conduit 26 through its louvres 30 or in the space between the two conduits, until it exits outside the muffler through the tailpipe 18.

The present invention also comprehends increasing the sound absorption capacity of the muffler by including a sound dampening or attenuating material or substrate 34 in at least one of the exhaust gas outlet 18 or the sound reducing element 26.

The substrate 34 will preferably have pores or other features to allow the exhaust gases to pass through the material. The use of the substrate 34 enables the muffler design to be simplified, or alternatively greater sound reduction to be achieved for the same design. For example, the addition of dampening material may remove the need for a baffle in the chamber 16. It can be appreciated that by omitting a baffle that would otherwise be present, the assembly process of the muffler is simplified.

The substrate 34 is preferably placed in the tailpipe 18 closer to the back wall 20. However, the invention comprehends placing the substrate 34 anywhere in the tailpipe 18, or alternatively in the conduit 26. FIGS. 3-5 show several embodiments of the modular muffler having the dampening material or substrate 34. In FIG. 3, the tailpipe 18 has a wider section 36 adjacent to back wall 20. The substrate 34 is in the wider section 36, and louvres 30 are present only in the portion of the tailpipe 18 between the substrate 34 and back wall 20. It can be seen that exhaust gas 11 enters tailpipe 18 at louvres 30 and then passes through substrate 34 and into the inner conduit 26. The inner conduit 26 has a baffle 27, so that the exhaust gases flow around the baffle, through louvres 30 on the conduit 26, and out of the tailpipe 18. The section 36 is preferably wider than the diameter of the rest of the tailpipe 18 to enable a freer flow of gas 11 and to permit use of a larger substrate 34. In the embodiment of FIG. 4 the substrate 34 is placed outside the tailpipe 18, with louvres 30 again only present between the substrate 34 and back wall 20. In this case the gas 11 first passes through the substrate 34 and then enters the tailpipe. Again, the exhaust gases flow around baffle 27 to exit the tailpipe. Finally, FIG. 5 shows an embodiment where substrate 34 is inside the inner conduit 26 rather than the tailpipe 18.

A further benefit of the substrate 34 is that it can be coated to form a catalytic converter 38. When the muffler is heated during operation, the catalytic converter burns previously unburnt carbon particles. The catalytic converter therefore provides the benefit of reducing pollution from the engine exhaust. Use of the catalyst accordingly enables broader use of the muffler in jurisdictions where emission control technology is required. The catalytic converter 38 may also be placed in the exhaust inlet 14, as shown for example in FIG. 5.

It can be appreciated that the modular muffler of the present invention can be manufactured using standard production techniques. The base muffler 12 is generally configured similar to other mufflers in common use. Further, configuring the base muffler 12 to receive the conduit 26 can generally also be readily implemented. For example, sizing the diameter of the tailpipe 18 to receive a conduit 26 having sealing rings 28 requires selection of an appropriate sized tailpipe, but no specific additional methods or techniques.

The conduit 26 is similarly generally convenient to produce, being merely a conduit or tube in its preferred embodiment. The conduit 26 is preferably welded to back wall 20 by welding along the outside of the wall 20. The muffler 10 is preferably made from a common material such as steel, similar to other mufflers. Finally, the manufacturing of a muffler having an uncoated substrate 34 is the same as for a catalytic converter 38, since the only difference is the presence of a coating on the catalytic converter 38.

The operation of the present invention can now be described. The manufacturer of a vehicle or device that uses a muffler will install the base muffler 12 by securing it to the body of the vehicle and connecting the engine exhaust outlet to the exhaust gas inlet or inlets 14. This will generally be a standard procedure since the base muffler will be similar to conventional mufflers in this regard. Once installed, the muffler will produce a measured degree of sound reduction in accordance with its particular configuration.

Where it is desired to obtain a higher degree of sound reduction, the manufacturer, distributor, or even user of the muffler will insert the conduit 26 into the tailpipe 18. In the preferred embodiment, the unexpanded seal rings will form a light friction fit with the inside of the tailpipe so that the installer can slide the conduit 26 without too much difficulty. The conduit 26 will preferably be pushed in as far as it can go, so that the spark arrestor 32 will project just past the termination point 24 of the tailpipe 18.

Upon the next start-up of the vehicle or device, the muffler 10 will heat up causing the seal rings 28 to expand, locking the conduit 26 in place. Where the attachment means 28 are some other means, the installer may need to further secure the conduit 26, such as by tightening a bolt or screw, or rotating the conduit to match a pin with a slot. Once the conduit 26 is secured, by whatever attachment means, preferably no further work will need to be done to maintain the muffler.

Accordingly, it can be appreciated that the muffler 10 of the present invention provides a means to modify the sound attenuation level of a muffler after the muffler has been produced and sealed. The modification is easily performed from outside the muffler without having to open the muffler or otherwise tamper with its structural integrity. By selecting from a variety of inner conduits 26 each having a different configuration of sound reduction features, a predetermined sound output level out of a range of values can be obtained from a single base muffler design.

Thus, one base muffler design can be easily fitted to a range of motor sizes, or meet a range of noise specifications, by the selection of an appropriate sound reducing member. The present invention provides that such sound reduction can be achieved without an unacceptable increase in back pressure. Thus, the louvres, baffles, and other components are sized and shaped to reduce sound on the one hand but not to unacceptably increase back pressure on the other.

It will be appreciated by those skilled in the art that the foregoing description was in respect of preferred embodiments and that various alterations and modifications are possible within the broad scope of the appended claims without departing from the spirit of the invention. For example, while reference is made to the attachment of a single sound reducing element, additional sound reducing elements might also be attached to achieve further sound reduction. Various other modifications will be apparent to those skilled in the art but are not described in any further detail herein.

The above disclosure is intended to be illustrative and not exhaustive. This description will suggest many variations and alternatives to one of ordinary skill in this art. All these alternatives and variations are intended to be included within the scope of the claims where the term “comprising” means “including, but not limited to”. Those familiar with the art may recognize other equivalents to the specific embodiments described herein which equivalents are also intended to be encompassed by the claims.

Further, the particular features presented in the dependent claims can be combined with each other in other manners within the scope of the invention such that the invention should be recognized as also specifically directed to other embodiments having any other possible combination of the features of the dependent claims. For instance, for purposes of claim publication, any dependent claim which follows should be taken as alternatively written in a multiple dependent form from all prior claims which possess all antecedents referenced in such dependent claim if such multiple dependent format is an accepted format within the jurisdiction (e.g. each claim depending directly from claim 1 should be alternatively taken as depending from all previous claims). In jurisdictions where multiple dependent claim formats are restricted, the following dependent claims should each be also taken as alternatively written in each singly dependent claim format which creates a dependency from a prior antecedent-possessing claim other than the specific claim listed in such dependent claim below.

This completes the description of the preferred and alternate embodiments of the invention. Those skilled in the art may recognize other equivalents to the specific embodiment described herein which equivalents are intended to be encompassed by the claims attached hereto. 

1. An exhaust gas muffler for an engine, said exhaust gas muffler having a body; at least one inlet for said exhaust gas from said engine on said body; a chamber in said body to receive exhaust gas from said at least one exhaust gas inlet and to reduce a sound of said exhaust gas; and at least one exhaust gas outlet from the chamber to vent said exhaust gas from said chamber, said exhaust gas outlet being sized and shaped to receive a sound reducing element from outside of said muffler; wherein, by attaching a sound reducing element to said muffler, said muffler can reduce said sound of said exhaust gas to a predetermined level.
 2. The exhaust gas muffler according to claim 1, further including a sound reducing element attached to said exhaust gas outlet, to further reduce said sound of said exhaust gas.
 3. The exhaust gas muffler according to claim 2, wherein said exhaust gas outlet is a first conduit having a diameter, and said sound reducing element is a second conduit having a diameter less than said diameter of said first conduit.
 4. The exhaust gas muffler according to claim 2, wherein at least one of said exhaust gas outlet and said sound reducing element includes an attachment means to secure said sound reducing element to said exhaust gas outlet.
 5. The exhaust gas muffler according to claim 2, wherein at least one of said exhaust gas outlet and said sound reducing element includes a dampening material to increase the sound absorption capacity of said muffler.
 6. A sound reducing element for an engine exhaust gas muffler, said sound reducing element having a body, said body being sized and shaped to fit inside an exhaust gas outlet of said muffler, said body having sound reduction properties; and an attachment means to secure said body to said exhaust gas outlet.
 7. A method of increasing the sound absorption capacity of an exhaust gas muffler, said method comprising providing a sound reducing element sized and shaped to attach to an exhaust gas outlet of said muffler; inserting said sound reducing element inside said exhaust gas outlet; and securing said sound reducing element to said exhaust gas outlet. 